* API: BREAKING CHANGE: (bug 11430) Return fewer results than the limit in some cases to prevent running out of memory
* This means queries could possibly return fewer results than the limit and still set a query-continue
* Add iicontinue, rvcontinue, cicontinue, incontinue, amfrom to faciliate query-continue for these modules
* Implemented by blocking additions to the ApiResult object if they would make it too large
** Important things like query-continue values and warnings are exempt from this check
** RSS feeds and exported XML are also exempted (size-checking them would be too messy)
** Result size is checked against $wgAPIMaxResultSize, which defaults to 8 MB

For those who really care, per-file details follow:

ApiResult.php:
* Introduced ApiResult::$mSize which keeps track of the result size.
* Introduced ApiResult::size() which calculates an array's size
(which is the sum of the strlen()s of its elements).
* ApiResult::addValue() now checks that the result size stays below
$wgAPIMaxResultSize. If the item won't fit, it won't be added and addValue()
will return false. Callers should check the return value and set a
query-continue if it's false.
* Closed the back door that is ApiResult::getData(): callers can't manipulate
the data array directly anymore so they can't bypass the result size limit.
* Added ApiResult::setIndexedTagName_internal() which will call
setIndexedTagName() on an array already in the result. This is needed for the
'new' order of adding results, which means addValue()ing one result at a time
until you hit the limit or run out, then calling this function to set the tag
name.
* Added ApiResult::disableSizeCheck() and enableSizeCheck() which disable and
enable size checking in addValue(). This is used for stuff like query-continue
elements and warnings which shouldn't count towards the result size.
* Added ApiResult::unsetValue() which removes an element from the result and
decreases $mSize.

ApiBase.php:
* Like ApiResult::getData(), ApiBase::getResultData() no longer returns a
reference.
* Use ApiResult::disableSizeCheck() in ApiBase::setWarning()

ApiQueryBase.php:
* Added ApiQueryBase::addPageSubItem(), which adds page subitems one item
at a time.
* addPageSubItem() and addPageSubItems() now return whether the subitem
fit in the result.
* Use ApiResult::disableSizeCheck() in setContinueEnumParameter()

ApiMain.php:
* Use ApiResult::disableSizeCheck() in ApiMain::substituteResultWithError()
* Use getParameter() rather than $mRequest to obtain requestid

ApiQuerySiteinfo.php:
* Abuse siprop as a query-continue parameter and set it to all props that
couldn't be processed.

ApiQueryRandom.php:
* Doesn't do continuations, because the result is supposed to be random.
* Be smart enough to not run the second query if the results of the first
didn't fit.

ApiQueryImageInfo.php, ApiQueryRevisions.php, ApiQueryCategoryInfo.php, ApiQueryInfo.php:
* Added continue parameter which basically skips the first so many items

ApiQueryBacklinks.php:
* Throw the result in a big array first and addValue() that one element at a time if necessary
** This is necessary because the results aren't retrieved in order
* Introduced $this->pageMap to map namespace and title to page ID
* Rewritten extractRowInfo() and extractRedirRowInfo() a little
* Declared all private member variables explicitly

ApiQueryDeletedrevs.php:
* Use a pagemap just like in Backlinks
* Introduce fake page IDs and keep track of them so we know where to add what
** This doesn't change the output format, because the fake page IDs start at 0 and are consecutive